Ecology is the study of interactions among organisms and their environment.

Ecologists are scientists who study these relationships. Ecologists divide the environmental factors that influence organisms into two groups (abiotic and biotic factors). Many times, ecologists must travel to specific environments to examine the organisms that live there.

Abiotic factors are the nonliving parts of the environment.

Water is needed by all organisms for cell and life processes.

Light and temperature determine where plants and animals can live.

Air gases such as oxygen, nitrogen, and carbon dioxide are needed by most species.

Soil types determine what plants and animals can live in an area. Soil provides a home for many species of animals.

Biotic factors are living or once-living parts of the environment.

All members of one species living together form a population.

Communities are groups of populations that interact with each other in a given area.

An ecosystem is the biotic community and its abiotic factors. Examples of ecosystems include coral reefs, forests, and ponds.

Biomes are large areas containing several ecosystems.

The biosphere includes the top layer of the Earth’s crust, all waters, and the atmosphere.

Characteristics of Populations

The population size is the number of individuals in a population. The size of a population is always changing.

The size of the human population is increasing each year.

The population density is the number of individuals in a particular area.

This shows the population density of the northern bobwhite birds in the United States.

Population Spacing is how organisms are arranged in an area. Evenly Spaced- consistent distance between organisms Randomly Spaced- individual location is independent of other individuals’ locations (wind/birds disperse seeds) Clumped Spacing- organisms group together (herds, flocks)

A limiting factor is a biotic or abiotic factor that restricts the size of a population. Food can be a limiting factor if the amount of food can only support a certain number of an animal in a population.

The carrying capacity is the maximum population size that can live in an environment over time.

The biotic potential is the size a population could reach if no limiting factors stopped its growth. Most populations never reach their biotic potential.

Symbiosis is the close interactions between species. Symbiotic relationships can be identified by the type of interaction between organisms.

Symbiosis A symbiotic relationship that benefits both species, it is termed mutualism. ex: moth and yucca plant Commensalism is a form of symbiosis that helps one species but has no effect on the other. Ex: flatworms and horseshoe crabs When one species is harmed and the other benefits, it is parasitism. Ex: some mistletoe and trees

Predation- occurs when one species hunts, kills, and eats another organism. Owls use their senses of sight and hearing to hunt for mice (their prey) in the dark.

Habitat- where the organism lives Niche- an organism’s function in its ecosystem. It can also be described as its role or job in the ecosystem.

An earthworm’s habitat is soil. An earthworm’s niche includes loosening, aerating, and enriching the soil.